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Q: Does CO2 Leak Naturally from the Earth?

A: All the time!

The bubbles in the photograph at right are made by carbon dioxide naturally leaking from underneath a lake in Maria Laach, Germany. For thousands of years CO2 has bubbled to the water’s surface and mixed with the air. Plants, animals, and humans still live on the shores of the lake.

In Perrier, France, another natural CO2 leak produces the carbonated water that is packaged into green bottles and sold all over the world.

And carbon dioxide is discharged from some volcanos when they erupt.

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A: Carbon dioxide constantly leaks into the environment from natural sources, and that's good for scientists.

Natural CO2 analogues are useful to scientists trying to understand what kind of environmental signals a carbon dioxide leak would make.

In Germany, for example, scientists have found that certain plants grow better near the natural CO2 leaks.

In Italy, researchers have found that carbon dioxide mixes with water forming a weak acid that releases electrically-charged ions that can be detected with electromagnetic measurements of the soil.

The crystal geyser near the Green River in Utah is a rare example of a cold geyser. In most geysers, the force of hydrothermal energy sends water spouting into the air, but at crystal geyser it's pressurized carbon dioxide that provides the force. Scientists have characterized the signals the carbon dioxide leaves in the rock formations and in the groundwater.

In Texas, scientists are studying how the composition of different gases change when carbon dioxide leaks into the soil from industrial sources compared to natural sources. They have found that if the ratio of oxygen to carbon dioxide is less than 1:1, it's a signal carbon dioxide could be leaking into the soil from a source that's not natural.

While natural analogues provide insight into CO2 leaks, they are also different from the type of leak that could occur from a carbon sequestration project.

Natural analogues can’t be controlled like carbon sequestration projects can. If a problem is detected in a carbon sequestration site, injection can be stopped. In nature, there’s no way to limit the source of carbon dioxide.

The physical structure can differ at natural analogue and at sequestration sites. Sequestration sites are carefully chosen so that the rocks where the carbon dioxide is stored retains the CO2 by several different processes. Natural analogues occur in places where the geological formations do not contain CO2 very well.

The icon on the left links to work done by Italian researchers at comparing environmental signals at a natural analogue and industrial carbon storage sites.

In Chimayo, New Mexico, researchers from Los Alamos National Labs are studying how carbon dioxide that naturally flows through aquifers may impact drinking water.

Romanak and her colleagues are using a type of natural analogue called a playa lake to understand how carbon dioxide reacts with the environment. To view a presentation she gave on the topic, click left.